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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This package implements the SHA1 hash algorithm as defined in RFC 3174.
package sha1
import (
"hash";
"os";
)
// The size of a SHA1 checksum in bytes.
const Size = 20
const (
_Chunk = 64;
_Init0 = 0x67452301;
_Init1 = 0xEFCDAB89;
_Init2 = 0x98BADCFE;
_Init3 = 0x10325476;
_Init4 = 0xC3D2E1F0;
)
// digest represents the partial evaluation of a checksum.
type digest struct {
h [5]uint32;
x [_Chunk]byte;
nx int;
len uint64;
}
func (d *digest) Reset() {
d.h[0] = _Init0;
d.h[1] = _Init1;
d.h[2] = _Init2;
d.h[3] = _Init3;
d.h[4] = _Init4;
d.nx = 0;
d.len = 0;
}
// New returns a Hash computing the SHA1 checksum.
func New() hash.Hash {
d := new(digest);
d.Reset();
return d;
}
func (d *digest) Size() int { return Size }
func (d *digest) Write(p []byte) (nn int, err os.Error) {
nn = len(p);
d.len += uint64(nn);
if d.nx > 0 {
n := len(p);
if n > _Chunk - d.nx {
n = _Chunk - d.nx;
}
for i := 0; i < n; i++ {
d.x[d.nx + i] = p[i];
}
d.nx += n;
if d.nx == _Chunk {
_Block(d, &d.x);
d.nx = 0;
}
p = p[n:len(p)];
}
n := _Block(d, p);
p = p[n:len(p)];
if len(p) > 0 {
for i := 0; i < len(p); i++ {
d.x[i] = p[i];
}
d.nx = len(p);
}
return;
}
func (d *digest) Sum() []byte {
// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
len := d.len;
var tmp [64]byte;
tmp[0] = 0x80;
if len%64 < 56 {
d.Write(tmp[0 : 56 - len%64]);
} else {
d.Write(tmp[0 : 64 + 56 - len%64]);
}
// Length in bits.
len <<= 3;
for i := uint(0); i < 8; i++ {
tmp[i] = byte(len>>(56 - 8*i));
}
d.Write(tmp[0:8]);
if d.nx != 0 {
panicln("oops");
}
p := make([]byte, 20);
j := 0;
for i := 0; i < 5; i++ {
s := d.h[i];
p[j] = byte(s>>24);
j++;
p[j] = byte(s>>16);
j++;
p[j] = byte(s>>8);
j++;
p[j] = byte(s);
j++;
}
return p;
}
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